With the news that Jarred Tinordi signed a one-year deal with the club, the Canadiens have nine NHL-calibre defensemen on the roster. If you accept that Jeff Petry, P.K. Subban, Nathan Beaulieu, and Andrei Markov will compose the top two pairings, that leaves Tom Gilbert, Alexei Emelin, Mark Barberio, Greg Pateryn and Jarred Tinordi fighting for the two remaining spots.
Ideally, the Canadiens would trade Alexei Emelin and his $4.1M cap hit, but considering many teams in the league are struggling to clear salary cap space, that's probably not a realistic scenario.